1. Field of the Invention
The present invention relates to a synchronous control device used in processing systems for stretching resins and metals, conveyors and rotary presses. The present invention particularly relates to a synchronous control device which provides an origin matching operation in order to synchronously drive rotational phase and rotational frequency of electric motors in a master section and plural slave sections as well as synchronously drive the rotational phase and the rotational frequency of each machine shaft driven by said electric motors.
2. Description of the Related Art
FIGS. 23(a), (b) illustrate an example of a conventional rotary press with shafts. FIG. 23(a) illustrates a driving system of the conventional rotary press and is comprised of the following components, a main shaft 100, an electric motor 101, a sub shaft 102, a transmitter or a deceleration device 103, a paper feeding part 104, a printing part 105, color printing parts of yellow 106, cyan 107, magenta 105 and black 109, running paper 110, and a folding part 111.
In FIG. 23(a) each running paper 110 from the paper feeding part 104 is printed in the printing parts 105xcx9c106 and gathered to be folded in the folding part. Here, in the conventional rotary press, the printing parts 105xcx9c109 and the folding part 111 are mechanically combined and synchronously driven with the main shaft 100 and the sub shaft 102 which are driven by the plural electric motors.
FIG. 23(b) diagrams a model of the printing part 105xcx9c109, in which ink is supplied from an ink roller 105a to an image part of a lithographic plate which is wound on a plate cylinder 105b. The ink which is supplied to the image part of a lithographic plate is transferred to a face on a blanket cylinder 105c, then it is printed on the paper 105d. The printing position of each paper should be precisely accorded in the folding part 111. Since the printing parts 106xcx9c109 conduct color print, the printing position in the color printing parts 106xcx9c109 especially should be accorded each other with high accuracy because a shear of only 20xcx9c30 xcexcm in printing produces visual color misalignment.
According to the present invention, as plural electric motors can be synchronously controlled with high precision, a shaft-less rotary press can be realized in place of the conventional rotary press driven with shafts.
A master electric motor, a slave electric motor and a conventional synchronous control device driven by these electric motors are shown in the following.
FIG. 24 illustrates an example of a conventional synchronous control device for plural electric motors. For simplicity, this diagram is comprised of a master section and one slave section.
In FIG. 24, 0 is a master section, 1 is a slave section, 01 is a rotational frequency setting device, Cm is a master control device, 11 is a rotational frequency detector, 12 is a rotational frequency feedback detector, 13 is a gain amplifier, Am is a master driving device, Im is a master electric motor, Rm is a master rotary encoder, Km is a shaft of the master machine, Cs1 is a slave control device, 21, 23, 26 and 28 are receiving interfaces, 22 is a rotational frequency detector, 24 is a rotational frequency feedback detector, 25 is a gain amplifier, 27 is a phase detector of the master electric motor, 29 is a phase detector of the slave electric motor, 30 is a phase deviation detector for the electric motors, 31 is a gain amplifier, 40 is a switch for a synchronous control, As1 is a slave driving device, Is1 is a slave electric motor, Rs1 is a slave rotary encoder and Ks1 is a shaft of the slave machine.
The master rotary encoder Rm and the slave rotary encoder Rs1 output A phase pulse and B phase pulse in proportion to the rotation and output Z phase pulse per each rotation.
In FIG. 24, a signal from the rotational frequency setting device 01 is sent to the rotational frequency detector 11 of the control device Cm of the master section. The rotational frequency feedback detector 12 detects rotational frequency feedback according to the A phase signal and the B phase signal outputted from the master rotary encoder Rm attached to the master electric motor Im.
The output signals from the rotational frequency detector 11 and the rotational frequency feedback detector 12 are calculated and sent to the master driving device Am through the gain amplifier 13. The master driving device Am then drives the master electric motor Im by controlling rotational frequency, and the shaft Km of the master machine is driven.
The A phase signal and B phase signal from the master rotary encoder Rm are also sent to the rotational frequency setting detector 22 through the receiving interface 21 of the slave control device Cs1 so as to detect a setting rotational frequency of the slave section 1. Addition, A phase signal and B phase signals outputted from the slave rotary encoder Rs1 attached to the slave electric motor are sent to the rotational frequency feedback detector 24 through the receiving interface 23 of the slave control device Cs1 in order to detect a rotational frequency feedback. The output signals from the rotational frequency detector 22 and the rotational frequency feedback detector 24 are calculated and sent to the slave driving device As1 through the gain amplifier 25. The slave driving device As1 drives the slave electric motor Is1 so as to tune the master electric motor Im and the shaft Km of the master machine and the shaft Ks1 of the slave machine are driven in tune.
Furthermore, the phase detector 27 of the master electric motor in the slave control device Cs1 counts the A phase pulse and B phase pulse outputted by the rotation of the master electric motor Im through the receiving interface 21 and clears the phase detector 27 by Z phase signal outputted by each rotation of the master electric motor Im through the receiving interface 26. The phase detector 27 of the master electric motor constantly detects the rotational phase of the master electric motor and that of the shaft of the master machine with the number of pulses.
In the same manner, the phase detector 29 of the slave electric motor counts up the A phase pulse and B phase pulse outputted by the rotation of the slave electric motor Is1 through the receiving interface 23, and clears them by Z phase signal outputted by each rotation of the slave electric motor Is1, through the receiving interface 28. The phase detector 29 of the slave electric motor constantly detects rotational phase of the slave electric motor and the shaft of the slave machine with number of pulses.
Then the output of the phase detector 27 of the master electric motor and the phase detector 29 of the slave electric motor are inputted to the phase deviation detector 30 so as to calculate the phase deviation and output it. The phase deviation goes through the gain amplifier 31 and switch 40, which is closed when synchronous control is ON, and it is added to or subtracted from the output of the rotational frequency detector 22 as correction, then the synchronous control is performed.
Here, referring to FIG. 26, the phase deviation outputted from the phase deviation detector 30 according to the prior art is explained.
In FIG. 26, X axis shows difference of the rotational number between the master electric motor Im and the slave electric motor Is1, Y axis shows a phase deviation, which is outputted from the phase deviation detector 30, converted to angle. In FIG. 26-A, a circle (a) shows the modeled shaft Km of the master machine, a line z1 shows projection of Z phase position of the master rotary encoder Rm on the circle (a). In this invention, counterclockwise direction is defined as an ordinary direction of the electric motors, that is, from the center of the circle (a), which shows the shaft of the master machine Km, plus(+) direction of the x axis=0xc2x0, plus(+) direction of the y axis=+90xc2x0, minus(xe2x88x92) direction of the x axis=+180xc2x0, minus(xe2x88x92) direction of the y axis=+270xc2x0. In the same manner, in FIG. 26-B, a circle (b) shows the shaft Ks1 of the slave machine and z1 shows Z phase of the slave rotary encoder Rs1.
FIGS. 26-A and B illustrate that the shaft Km of the master machine is 90xc2x0 behind compared to the shaft Ks1 of the slave machine, and a phase deviation is xe2x88x9290xc2x0 as shown by a point P. FIGS. 26-C and D illustrate that the shaft Km of the master machine is 90xc2x0 forward compared to the shaft Ks1 of the slave machine, and a phase deviation is +90xc2x0 as shown by a point Q. More over, FIGS. 26-E and F illustrate that the shaft Km of the master machine is 270xc2x0 forward compared to the shaft Ks1 of the slave machine, however the phase deviation becomes smaller if the shaft Km of the master machine is 90xc2x0 behind compared to the shaft Ks1 of the slave machine, it is shown by a point R in FIG. 26-E.
As mentioned above, the phase deviation of rotation is detected normally in the range from xe2x88x92180xc2x0 to +180xc2x0, the output of the phase deviation detector 30 for the electric motors of FIG. 24 is shown in FIG. 26.
Next, the action in the FIG. 24 is explained with reference to FIG. 25.
In FIG. 25-A, same as FIG. 26-A, a circle (a) shows the shaft Km of the master machine, a line z1 shows a Z phase position of the master rotary encoder Rm. Also, in FIG. 25-B, a circle (b) shows the shaft Ks1 of the slave machine, a line z1 shows a Z phase position of the slave rotary encoder Rs1.
C27 and C29 show time transition by converting the output of the phase detector 27 of the master electric motor and the output of the phase detector 29 of the slave electric motor to angle, respectively.
FIG. 25-A illustrates a phase of the shaft Km of the master machine at time t1 is, for example, 0xc2x0, FIG. 25-B illustrates a phase of the shaft Ks1 of the slave machine at time t1 is, for example, +270xc2x0. The output C27 of the phase detector 27 of the master electric motor and the output C29 of the phase detector 29 of the slave electric motor shown in FIG. 24 are corresponded to C27=0xc2x0 in FIG. 25-A and C29=0xc2x0 in FIG. 25-B, at time t1, respectively.
At time t1, the slave electric motor Is1 is driven so as to tune with the master electric motor Im (the rotational frequency of the slave electric motor Is1 is controlled so as to be in accord with it of the master electric motor Im). At time t2 the switch 40 is closed, a synchronous control is ON. At time t2, when the phase of the shaft Km of the master machine in FIG. 25-C is, for example, +225xc2x0, the phase of the shaft Ks1 of the slave machine in FIG. 25-D is, for example, +135xc2x0, the phase deviation detected by phase deviation detector 30 for the electric motors is converted to angle xcex94xcex8t2.
xcex94xcex8t2=225xe2x88x92135=90xc2x0xe2x80x83xe2x80x83(1)
After time t2, the switch 40 is closed and the synchronous control is ON, an origin matching is started. By correcting the phase deviation which is detected in the same manner of the equation (1), constantly, the phase detector 29 of the slave electric motor changes phase as shown C29, C27 in FIG. 25 so as to get near the phase of the phase detector 27 of the master electric motor, at time t3 the origin matching is completed then the master electric motor Im and the slave electric motor Is1 are shifted to a synchronous control.
FIGS. 25-E, F illustrate the situation that the master section and the slave section are controlled synchronously at time t4. FIG. 25-I modeledly illustrates that the output of the phase detector 27 of the master electric motor and the output of the phase detector 29 of the slave electric motor are almost overlapped each other, because the master section and the slave section are driven synchronously.
In FIG. 24, the master section 0 and the slave section 1 detect an absolute position by the phase detector 27 of the master electric motor and the phase detector 29 of the slave electric motor, respectively, so as to detect a phase deviation by these phase detectors. In this invention it is called xe2x80x9ca method for correcting an absolute phase deviationxe2x80x9d.
In this method of correcting an absolute phase deviation, under synchronous control an origin can be matched without any means even when the shaft Km of the master machine and the shaft Ks1 of the slave machine are in any phase relation.
Here, an origin matching is defined as a period from the time when the synchronous control is ON till the time when a phase deviation becomes within xc2x1xcex52 pulse (for example, xc2x1xcex52=xc2x15), if an objective accuracy of the synchronous control is xc2x1xcex52 pulse.
Here, when an electric motor and a machine shaft are connected, a deceleration device is sometimes employed because of the structure, installation space or capacity of the electric motor. FIG. 27 illustrates a synchronous control device according to the conventional synchronous control in the case that the deceleration device is employed. FIG. 28 and FIG. 29 illustrate the action of the origin matching.
The difference between FIG. 27 and the aforementioned FIG. 24 is that the master electric motor Im and the slave electric motor Is1 are connected to the shaft Km of the master machine and the shaft Ks1 of the slave machine with deceleration device Gm and Gs1, respectively. In FIG. 27, the same parts which have the same action shown in FIG. 24 are referred to using the same symbols. The explanations thereof are abridged.
FIG. 28 illustrates an action when a synchronous control by the conventional synchronous control device shown in FIG. 27 is performed. In the following, in order to simplify the explanation, the deceleration ratio (1/N) of the slave deceleration device Gs1 is 1/4 (N=4) to the master deceleration device Gm.
In FIG. 28-A, a circle (a) shows the modeled shaft Km of the master machine and lines z1, z2, z3 and z4 show projection of the z-phase positions of the master rotary encoder Rm on the circle (a). The line z1 is shown with thick line as a base of one rotation of the shaft Km of the master machine. The numbers 1, 2, 3 and 4 show that 4 rotations of the master electric motor Im make one rotation of the shaft Km of the master machine.
In the same manner, in FIG. 28-B, a circle (b) shows the shaft Ks1 of the slave machine and lines z1 , z2, z3 and z4 show projection of the z-phase positions of the slave rotary encoder Rs1 on the circle (b). The numbers {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} show that 4 rotations of the slave electric motor Is1 make one rotation of the shaft Ks1 of the slave machine.
Also, in FIG. 28, C27 and C29 show time transition by converting the output of the phase detector 27 of the master electric motor and the output of the phase detector 29 of the slave electric motor to angle, respectively.
In FIG. 28, the master electric motor Im and the slave electric motor Is1 are driven under tuning control. At time t1 when the switch 40 is closed and a synchronous control is ON.
At time t1 when the synchronous control is started, in FIG. 28-A, phase xcex8m (z1 phase as a basis) of the shaft Km of the master machine is, for example, xcex8m=+270xc2x0 in the shaft of the electric motor(+270xc2x0/4=67.5xc2x0 in the shaft of machine). In FIG. 28-B, phase xcex8s1 (z1 phase as a basis) of the shaft Ks1 of the slave machine is, for example, xcex8s1=+180xc2x0 in the shaft of the electric motor(+180xc2x0/4=45xc2x0 in the shaft of machine). They correspond to the output C27=270xc2x0 of the phase detector 27 of the master electric motor and the output C29=180xc2x0 of the phase detector 29 of the slave electric motor, respectively.
After time t1 when the synchronous control is ON, C29 is controlled so as to get near C27, then C27 and C29 are overlapped at time t2 as shown in FIG. 28-I. At time t2, when 1, 2, 3 and 4 in FIG. 28-C and {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} in FIG. 28-D are in the same position, the origin matching is completed normally.
When the origins are matched normally, the phase deviation between the shaft Km1 of the master machine and the machine shaft Ks1 of the slave machine is xcex8mxe2x88x92xcex8s1=270xc2x0xe2x88x92180xc2x0=90xc2x0 in the shaft of the electric motor by using the aforementioned rotational phase xcex8m and xcex8s1 of the shafts of the electric motors. The origin matching is completed normally when the following equation is realized.
{the phase deviation when the synchronous control is ON=|xcex8mxe2x88x92xcex8s1|} less than 180xc2x0xe2x80x83xe2x80x83(2)
In the aforementioned example, the origin matching is completed normally even when the deceleration device is equipped. However as the phase relation between the shaft Km of the master machine and the shaft Ks1 of the slave machine is indefinite there are some cases that the origin matching is failed. FIG. 29 illustrates the case.
In FIG. 29 at time t1 when the synchronous control is ON, the shaft Km of the master machine is shown in FIG. 29-Axe2x80x2, for example, the phase of the shaft Km of the master machine is xcex8m=xe2x88x9290xc2x0 in the shaft of the electric motor (xe2x88x9290xc2x0/4=xe2x88x9222.5xc2x0 in the shaft of machine ). The shaft Ks1 of the slave machine is shown in FIG. 29-Bxe2x80x2, for example, the phase of the shaft Ks1 of the slave machine is xcex8s1=+180xc2x0 in the shaft of the electric motor (+180xc2x0/4=+45xc2x0 in the shaft of machine).
At time t1 when switch 40 is closed and the synchronous control is ON. After time t1, C29 shown in FIG. 29 is controlled so as to get near C27. Then at time t3, C29 is overlapped on C27 and the origin matching is completed as shown in FIG. 29-I.
Here, at time t3, xe2x80x9c2xe2x80x9d in FIG. 29-Cxe2x80x2 is synchronized with xe2x80x9c{circle around (3)}xe2x80x9d in FIG. 29-Dxe2x80x2. Therefore, the origin matching is completed in the state that the shaft Ks1 of the slave machine is 90xc2x0 forward compared to the shaft Km of the master machine though the master electric motor Im and the slave electric motor Is1 are synchronized.
In this case, when the synchronous control is ON in FIG. 29, the phase relation between the shaft Km1 of the master machine and shaft Ks1 of the slave machine is xcex8mxe2x88x92xcex8s1=xe2x88x9290xc2x0xe2x88x92180xc2x0=xe2x88x92270xc2x0 in the shaft of the electric motor by using the aforementioned rotational phase xcex8m and xcex8s1 of the shafts of the electric motors. The origin matching is failed when the following equation is realized.
180xc2x0 xe2x89xa6{(the phase deviation when the synchronous control is ON=|xcex8mxe2x88x92xcex8s1|}xe2x80x83xe2x80x83(3)
That is, in the synchronous control device employing the deceleration device with deceleration rate of 1/N (N is a positive integer) the origins are matched normally when the phase deviation between the master electric motor Im and the slave electric motor Is1 satisfies the aforementioned equation (2). However, when the phase deviation is in the aforementioned equation (3) a phase difference is caused in the origin is matching.
When the deceleration rate is, for example, 1/N=1/4, the phase difference of 90xc2x0, 180xc2x0, 270xc2x0 can be caused by the method for origin matching of the synchronous device shown in FIG. 27. In general, when the deceleration rate is 1/N any phase difference shown in the following equation (4) is caused.
360xc2x0/N
or
(360xc2x0xc3x972)/N
or
. 
. 
. 
{360xc2x0xc3x972(Nxe2x88x921)}/Nxe2x80x83xe2x80x83(4)
Also, in the case that the deceleration device is employed, the synchronous control is performed by the following equation as shown in the Japanese publication No. 6-311777.
The phase deviation xcex5=n1xc3x97N2xc3x97N1xc3x971/Zxe2x88x92n2xe2x80x83xe2x80x83(5)
In the aforementioned equation (5), N1 is a resolution of a master encoder, N2 is a resolution of a slave encoder, Z is a deceleration rate between the master machine and the slave machine, n1 and n2 are the number of pulses which are inputted per one scan of a control device from the rotary encoders of the master section and the slave section, respectively. The synchronous control according to the equation (5) detects relative differences between the number of pulses which is inputted per one scan of the master section and it of the slave section as correction. Here, this synchronous control is called xe2x80x9ca method for correcting a relative phase deviationxe2x80x9d.
In the aforementioned method for correcting a relative phase deviation, rotational frequency of the master section and it of the slave section can be tuned precisely, however the method doesn""t have mechanism of an origin matching. Also, if n1 or n2 in the aforementioned equation (5) are detected by error because of noises and so on, the phase relation between the master section and the slave section causes a difference and this difference is integrated.
As mentioned above, in the conventional synchronous control device employing a deceleration device between an electric motor and a machine shaft, there are some cases that an origin matching is failed according to the phase differences between a master electric motor and a slave electric motor when a synchronous control is ON.
An object of the present invention is that an origin matching between a shaft of a master machine and a shaft of a slave machine can be completed without causing a phase difference even when a deceleration device is employed, also the origin matching can be performed accurately when the master section and the slave section are driven even at low or high rotational frequency, or they are accelerated or decelerated, so that a very accurate synchronous control is performed rapidly and continuously.
The present invention solves the above-mentioned problems by the following way.
The present invention of claim 1 discloses a synchronous control device including a master section and a slave section for controlling a rotational frequency and a rotational phase between a master electric motor and a slave electric motor, or between a shaft of the master machine and a shaft of a slave machine which are driven by the respective electric motors, in the case that each deceleration device with a deceleration rate of 1/N (N is a positive integer) is employed between the master electric motor and the shaft of the master machine and between the slave electric motor and the shaft of the slave machine.
According to the present invention, a master rotary encoder for outputting pulses in response to the master electric motor, and an origin detector of the shaft of the master machine for detecting one rotation of the shaft of the master machine are provided.
Also, a slave rotary encoder for outputting pulses in response to the slave electric motor, and an origin detector of the shaft of the slave machine for detecting one rotation of the shaft of the slave machine are provided.
In the slave section, a rotational frequency detector for detecting a rotational frequency of the master electric motor by a signal outputted from the master rotary encoder is provided.
Also, a phase detector of the master electric motor for detecting rotational phase of the master electric motor by the output of the master rotary encoder and a phase detector of the slave electric motor for detecting the rotational phase of the slave electric motor by the output of the slave rotary encoder are provided.
Further, a phase detector of the shaft of the master machine for detecting a rotational phase of the shaft of the master machine by the output of a master rotary encoder and being cleared by the output of an origin detector of the shaft of the master machine, and a phase detector of the shaft of the slave machine for detecting the rotational phase of the shaft of the slave machine by the output of a slave rotary encoder and being cleared by the output of an origin detector of the shaft of the slave machine are provided.
Sill, a rotational frequency feedback detector for detecting a feed back rotational frequency of the slave electric motor by the signal outputted from the slave rotary encoder is provided.
Furthermore, according to the present invention, the first phase deviation detector for calculating the phase deviation between the shaft of the master machine and the shaft of the slave machine, and the second phase deviation detector for calculating the phase deviation between the master electric motor and the slave electric motor are provided.
The origin between the shaft of the master machine and the shaft of the slave machine is matched so as to control that, for example, the sum of the output of the first phase deviation detector and the difference between the output of the rotational frequency detector and the rotational frequency feedback detector gets smaller.
When the phase deviation between the shaft of the master machine and the shaft of the slave machine is within the predetermined value (for example, the phase deviation is xc2x11/2 rotational frequency of the shaft of the electric motor), continuously the origin between the master electric motor and the slave electric motor is matched so as to control that, for example, the sum of the output of the second phase deviation detector and the difference between the output of the rotational frequency detector and the rotational frequency feedback detector gets smaller.
According to the above-mentioned operation even when the deceleration devices are employed, the origin can be matched without causing any phase discrepancy of 360xc2x0/N, (360xc2x0xc3x972)/N, . . . {360xc2x0xc3x97(Nxe2x88x921)}/N (N is a positive integer) in the shaft of the slave electric motor. After the origin matching an accurate synchronous control can be started continuously even when the master machine and the slave machine are driven at any rotational frequency, of low or high, or decelerated.
Further, in the case that an incremental encoder is employed for the rotary encoder, the above-mentioned phase detectors are comprised of an integrating counter for detecting the phase of the shaft of the master machine, the phase of the shaft of the slave machine, the phase of the shaft of the master electric motor, and the phase of the slave electric motor, respectively.
For the phase detector of the electric motor, the pulse signal outputted from the rotary encoder are counted by the integrating counter, and the counted value is cleared by Z phase pulse outputted per one rotation of the rotary encoder.
For the phase detector of the shaft of the machine, the pulse signals outputted from the rotary encoder are counted by the integrating counter, then the counted value is cleared by the output of the origin detector of the shaft of the machine.
Also, in the case that an ablolute-type encoder is employed for the rotary encoder, the above-mentioned phase detectors are comprised of a register for detecting the phase of the shaft of the master machine, the phase of the shaft of the slave machine, the phase of the shaft of the master electric motor, and the phase of the slave electric motor, respectively.
For the phase detector of the electric motor, the signal corresponding to the rotational angle outputted from the absolute-type rotary encoder is always set in the register.
Also for the phase detector of the shaft of the machine, the register integrates the difference of the signal corresponding to the rotational angle outputted from the rotary encoder, and the integrated value is cleared by the output of the origin detector of the shaft of the machine.
According to the above-mentioned operation the rotational phase of the electric motor and the shaft of the machine in the master section and in the slave section can be detected accurately.
The present invention of claim 2 in the claim 1 discloses a phase shifter for correcting the output of the first phase deviation detector by a phase shift amount corresponding to a discrepancy between an angle of a shaft of a machine and an angle of a shaft of an electric motor.
By virtue of the phase shifter, as the discrepancy between an angle of a shaft of a machine and an angle of a shaft of an electric motor is canceled, the first origin matching between the shaft of the master machine and the shaft of the slave machine is shifted to the second origin matching between the master electric motor and the slave electric motor bumplessly.
That is, even when the relation between the Z-phase of the master rotary encoder and the origin of the shaft of the master machine is in any position in the master section, also even when that the relation between the Z-phase of the slave rotary encoder and the origin of the shaft of the slave machine is in any position in the slave section, as the correction can be performed by the phase shifter the control can be shifted to the synchronous control bumplessly.
The present invention of the claim 3 discloses a synchronous control device including a master section and a slave section for controlling a rotational frequency and the rotational phase between a master electric motor and a slave electric motor, or between a shaft of a master machine and a shaft of a slave machine driven by the respective electric motors, in the case that a deceleration device is employed only between the slave electric motor and the shaft of the slave machine.
According to the present invention, a master rotary encoder for outputting pulses in response to the master electric motor, and a slave rotary encoder for outputting pulses in response to the slave electric motor are provided.
Here, the output number of pulses or the maximum output value per one rotation of the master rotary encoder is N times (N is a positive integer) as many as the output number of pulses or the maximum output value per one rotation of the slave rotary encoder.
Also, an origin detector of the shaft of the slave machine for detecting one rotation of the shaft of the slave machine is provided.
In the slave section, a rotational frequency detector for detecting a rotational frequency of the master electric motor by a signal outputted from the master rotary encoder is provided.
Also, a phase detector of the master electric motor for detecting the rotational phase of the shaft of the master machine (namely, the shaft of the electric motor) by the output of a master rotary encoder and being cleared every one rotation of the master rotary encoder is provided. Further, a phase detector of the slave electric motor for detecting rotational phase of the slave electric motor by the output of the slave rotary encoder and being cleared every one rotation of the slave rotary encoder, and a phase detector of the shaft of the slave machine for detecting the rotational phase of the shaft of the slave machine by the output of the slave rotary encoder and being cleared by the output of the origin detector of the shaft of the slave machine are provided.
Still, a rotational frequency feedback detector for detecting a feed back rotational frequency of the slave electric motor by the signal outputted from the slave rotary encoder is provided.
Furthermore, according to the present invention, a first phase deviation detector for calculating the phase deviation between the shaft of the master machine and the shaft of the slave machine is provided.
Moreover, a master over counter and a slave over counter for outputting a coefficient value for converting a rotational phase of the slave electric motor to a phase corresponding to a rotational phase of the shaft of the slave machine is provided.
Furthermore, a second phase deviation detector for calculating the output of the phase detector of the master electric motor and the output of the phase detector of the slave electric motor, and the output of the master over counter and the output of the slave over counter, then outputting a phase deviation between the master electric motor and the slave electric motor is provided.
The origin between the shaft of the master machine and the shaft of the slave machine is matched so as to control that, for example, the sum of the output of the first phase deviation detector and the difference between the output of the rotational frequency detector and the rotational frequency feedback detector gets smaller.
When the phase deviation between the shaft of the master machine and the shaft of the slave machine is within the predetermined value (for example, the phase deviation is xc2x11/2 rotational frequency of the shaft of the electric motor), continuously the origin between the master electric motor and the slave electric motor is matched so as to control that, for example, the sum of the output of the second phase deviation detector and the difference between the output of the rotational frequency detector and the rotational frequency feedback detector gets smaller.
According to the above-mentioned operation, even when the deceleration devices are employed only in the slave section, same as the invention of claim 1, the origin can be matched without causing any phase discrepancy of 360xc2x0/N, (360xc2x0xc3x972)/N, . . . {360xc2x0xc3x97(Nxe2x88x921)}/N (N is a positive integer) in the shaft of the slave electric motor. After the origin matching, an accurate synchronous-control can be started continuously even when the master machine and the slave machine are driven at any rotational frequency, of low or high, or decelerated.
Further, in the case that an incremental rotary encoder is employed as a rotary encoder in the same manner as the invention of claim 1, an integrating counter may be employed as the phase detector. And in the case that an ablosute-type rotary encoder is employed as a rotary encoder, same as the invention of claim 1, a register may be employed.
According to the present invention of claim 4 in the claim 3, the master over counter and the slave over counter are initialized as follows;
That is, when the phase deviation for the electric motors is within the predetermined phase deviation,
in the case that the master section is forward compared to the slave section,
the counted value of the slave over counter is initialized to 0, 1 . . . (Nxe2x88x921) or xe2x88x921 corresponding to the output of the phase detector of the master electric motor and the phase detector of the slave electric motor, and the counted value of the master over counter is initialized to 0,
in the case that the master section is behind compared to the master section,
the counted value of the slave over counter is initialized to 0, 1 . . . (Nxe2x88x921) or N corresponding to the output of the phase detector of the master electric motor and the phase detector of the slave electric motor, and the counted value of the master over counter is initialized to 0.
According to the initialization, in the second phase deviation detector, the rotational phase of the slave electric motor is converted to the value corresponding the rotational phase of the shaft of the master machine, the rotational phase deviation of the electric motors can be found.
According to the present invention of the claim 5 in the claim 3 or the claim 4, when the master section and the slave section are under synchronous control the counted value of the master over counter and the slave over counter are renewed as follows;
That is, when the output of the phase detector of the master electric motor is cleared in the case that the counted value of the slave over counter is N or more, N is subtracted from the counted value of the slave over counter, in the case that the counted value of the over counter is less than N, 1 is added to the counted value of the master over counter.
When the output of the phase detector of slave electric motor is cleared in the case that the counted value of the slave over counter is (Nxe2x88x921) or more, (Nxe2x88x921) is subtracted from the counted value of the slave over counter and 1 is subtracted from the counted value of the master over counter, in the case that the counted value of the slave over counter is less than (Nxe2x88x921), 1 is added to the counted value of the slave over counter.
By the above-mentioned renewal, the phase deviation of the electric motors can be found in the second phase deviation detector.
According to the present invention of the claim 6 in the claim 3, the claim 4 and the claim 5, in stead of the master electric motor and the master rotary encoder, a concentrated control unit employing a phase generator for outputting phase setting signal based on N times the number of pulses corresponding to one rotation of the slave rotary encoder, and a transmitter for sending the output of the phase generator to the slave section is provided. Also, in the slave section, a receiver for inputting the output of the transmitter is provided so that a rotational frequency setting signal and a phase signal of the master electric motor are detected on the data of the receiver.
That is, as the electronically comprised phase generator is employed in the concentrated control unit, a stable signal can be generated and the slave electronic motor can be synchronously controlled accurately.
According to the present invention, as plural electric motors can be synchronously controlled with high precision, a shaft-less rotary press can be realized in place of the conventional rotary press driven with shafts.